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About the research

Assessing the structural integrity of bridge foundations is critical to ensuring the safety of the traveling public. However, nondestructive methods currently used in practice to determine the quality of drilled shaft foundations are severely limited by their inability to provide full coverage of the foundation cross-section, particularly in the critically-important region outside of the rebar cage.

The goal of this project is to evaluate the accuracy of a new thermal integrity profiling (TIP) technique for quality assurance of deep foundations. The TIP method utilizes infrared thermal probes lowered into access pipes, which are cast into the foundation to measure the heat of hydration of curing concrete. Previous studies demonstrated that the technique can detect loss of concrete cover outside the rebar cage, as well as internal flaws such as cracking or voids. However, the studies did not assess the accuracy of the technique for indicating the specific location and extent of flaws.

This research project is a collaborative effort between the Institute for Transportation (InTrans) at Iowa State University and the Iowa Department of Transportation (DOT) to evaluate the accuracy of the TIP method. A full-scale test shaft will be constructed with voids at predetermined locations. Measurements of shaft integrity will be compared for the new TIP method and the cross-hole sonic logging (CSL) method, which is currently the most commonly used quality assurance tool for drilled shafts.

The ability and accuracy of the two techniques to detect the specific locations, size, and general shape of the known shaft defects will then be assessed. It is anticipated that the thermal integrity profiling will provide cost savings to the Iowa DOT as a more economical alternative to CSL testing, or as a screening tool to identify which shafts should be further analyzed by CSL specialists.